Population is capped for citizens on the island, however it can support twice as many visitors. Visitors can wander around looking for salvage items and trading, buying and selling with locals. Visitors can not harvest any resources when visiting another island.
After a 6 month cool down period, from the date of purchase, islands purchased from the pirates may be sold back to the pirates for the original purchase price. You will probably get more for it at the auction ship though.
Ownership and authority are the only things that change when an island is sold. Land owners are not affected, other than possible governance change.
Once an island is sold to a fellow player, the pirates will not buy it back and it can only be sold to other players from that point forward.
Anyone that is not an island owner will have to either buy a block of land on someone else’s island or hang out on the cruise ship until land is gifted to them.
Islands are floating. You are only able to travel to any of the 10 random islands that surrounds the island that you are on. There is a “home” button that will instantly take you back to your house.